1. Field of the Invention
Aspects of the present invention relate to transmission lubrication and, in particular, to an assembly, and related systems and methods for externally providing lubrication to various internal components of a transmission.
2. Background of the Technology
A transmission is a device for transmitting the power generated by an engine, typically via a drive shaft connected to drive wheels on a vehicle. A conventional transmission provides for a variety of forward gears, as well as a neutral and a reverse gear. The typical components of an automatic transmission include a torque converter to allow a vehicle to stop while still in gear and with the engine running, a hydraulic system that pumps pressurized fluid through a valve body for controlling the planetary gear set through a series of clutches and bands, one or more planetary gear sets for providing the various gears, a governor to monitor speed and control shifting, and an oiling system for lubricating the many moving parts of the transmission assembly. A transmission housing or transmission case is also provided to protect and properly seal the various components internal thereto.
FIGS. 1-3 illustrate various aspects of a transmission assembly of the related art. For example, FIG. 1 illustrates an end view of an input shaft section 10 of a conventional transmission assembly, wherein an input shaft 20 is rotatably fitted with planetary gears 30 and a stator tube 40.
FIG. 2 is a partial sectional view of the input shaft section 10 taken along line C-C of FIG. 1, and generally depicts additional aspects of a related art transmission, including a high gear clutch and drum assembly 50, planetary section 60, a planetary output shaft 70, which may be integrally connected to the planetary section 60, a governor support 80, and a transmission case 90. As shown in FIG. 2, the stator tube 40 may comprise an elongated cylindrical tube portion 42 concentrically arranged around a forward portion of the input shaft 20, a flanged section 44, and a cylindrical hub section 46. The cylindrical hub section 46 may be formed with a sleeve bore 45 axially extending into the hub section 46 from a distal end 47 of the stator tube 40, the sleeve bore 45 having a larger inner diameter than an inner diameter of the tube portion 42. A stator tube sleeve 48 may be concentrically positioned around an outer surface of the input shaft 20 inside the sleeve bore 45. The stator tube sleeve 48 is configured with an inner diameter to minimize clearance between the stator tube sleeve 48 and the input shaft 20 while permitting free rotation of the input shaft 20 during operation of the transmission. The cylindrical hub section 46 may be formed with hub annulets 49 on an outer peripheral surface to provide seats for sealing rings, for example. The planetary gears 30 and the planetary section 60 may be coupled to an end portion of the input shaft 20, for example.
In the transmission of the related art shown in FIGS. 1-3, the interior components of the transmission receive a lubricating fluid, such as transmission oil, through a fluid passage 100. The fluid passage 100 may be cross-drilled, for example, into the flanged section 44 of the stator tube 40. The fluid passage 100 allows the pressurized lubrication fluid to flow radially inward toward the stator tube sleeve 48. As shown in FIG. 3, which is an enlarged view of the detail Section D, shown in dashed circle in FIG. 2, the stator tube sleeve 48 may comprise features, such as channels, grooves, protrusions, and/or through-holes, to direct and control the communication of lubricating fluid to particular areas or components of the transmission.
For example, as shown in FIGS. 2 and 3, the lubricating fluid communicates with the stator tube sleeve 48 by way of the fluid passage 100. As shown in FIG. 3, the stator tube sleeve 48 is formed and/or arranged so as to provide a gap 110 between the inner peripheral surface of the stator tube 40 and an outer peripheral surface of the stator tube sleeve 48. As the lubricating fluid travels through the gap 110, a channel 115 draws off some of the pressurized fluid to lubricate the components of the high gear clutch and drum assembly 50, for example, while the remaining fluid is forced through an opening 120 in the stator tube sleeve 48 and into an annular chamber 125.
As shown in FIG. 2, a transverse fluid passage 130 is provided that extends radially inward from the outer surface of the input shaft 20 and provides fluid communication between the annular chamber 125 and a central fluid passage 135. The central fluid passage 135 extends through the center of the input shaft 20 from a point at or near the transverse fluid passage 130 to an outlet 140 (see also FIG. 1) at one end of the input shaft 20. Lubrication openings 145 are provided at predetermined locations along the length of the input shaft 20 and extend radially from the central fluid passage 135 to the outer surface of the input shaft 20 to provide fluid communication between the central fluid passage 135 and the areas of the transmission containing the planetary gears 30, for example, and various other internal components, such as reverse clutches, washers, and rear case bushings and/or bearings. Thus, the pressurized fluid in the annular chamber 125 is forced through the transverse fluid passage 130 and into the central fluid passage 135, from which the pressurized fluid exits through the lubrication holes 145 and the outlet 140, to provide lubrication to the internal components of the transmission.
A shortcoming, among others, of the conventional transmission assembly of the related art described above is that the transmission lubrication system relies on internally feeding the lubricant (e.g., transmission fluid) to the various components through openings or passages in the shafts or components of the transmission. In particular, the many openings or passages in the input shaft 20 may significantly weaken the torque-bearing capability of the component and significantly introduce areas of substantial stress concentration, which may lead in turn to the eventual damage or failure of the input shaft 20.
There is an unmet need in the art for a transmission lubrication system that effectively lubricates the internal components of a transmission assembly without the need to provide openings, passages, or other weakening features, in the input shaft of the transmission assembly.